attribute vec4 a_Position; // attribute variable
uniform vec4 u_Transition;
uniform mat4 u_xformMatrix;
uniform mat4 projectionMatrix;
void main() {
  vec4 u_Position = u_xformMatrix * a_Position + u_Transition;
  gl_Position = projectionMatrix * u_Position;
  gl_PointSize = 2.0;
}